The iOS and OS X ecosystems may not be merging, but they're certainly better friends than before, with Apple's "Continuity" resulting in iDevices being able to finish off where the other left off, plus answer SMS and calls.
iPads, iPhones and Macs are now aware of each other when within proximity of each other. This means you can swipe Work or webpages from one device to another naturally, pulling content from one device to another, using Air Drop.
But the integration goes one step further again. A Mac can recognise you are writing an email on iPhone and prompt you to finish it on your computer. Your Mac can automatically recognise your iPhone as a hotspot if need be too, so long as you the devices are within range of each other.
SMS messages can be sent from a phone to a Mac too -- your iPhone acts as a relay to your computer, pushing regular texts and iMessages together. As can phone calls -- your Mac is now a speakerphone, letting you answer calls from the computer if your smartphone is out of reach, even if it's halfway across the house. You can dial a phone number direct from your Mac's contacts page, and even dial a number direct from your Mac, leveraging your iPhone's cellular connection.
From OS X Yosemite to iOS 8, here's everything Apple announced at WWDC